Seyfert, C. E. | bioRxiv Science

bioRxiv2024

Full-length structure of the host targeted bacterial effector Bep1 reveals a novel structural domain conserved in FIC effector proteins from Bartonella

Bacterial effector proteins translocated via a type-IV secretion system (T4SS) typically harbor a C-terminal segment required for recognition by the type-IV secretion coupling protein 1. In the -proteobacterial pathogen Bartonella, the signal is bipartite being composed of a BID (Bep intracellular delivery) domain and a positively charged C-terminal tail 2. Here, we show the crystal structure of full length Bartonella effector protein 1 (Bep1), which shows a novel FIC - OB - BAS(BID) domain arrangement conserved in the majority of Beps with the BID domain inserted into the newly discovered BAS parent domain. We propose that the BAS domain is necessary for the overall "boomerang"-like shape of Bep1 and that it plays a role during translocation through the T4SS.

microbiology↗

bioRxiv2024

Thermally activated antibiotic production by probiotic bacteria for pathogen elimination

Peptide drugs have seen rapid advancement in biopharmaceutical development, with over 80 candidates approved globally. Despite their therapeutic potential, the clinical translation of peptide drugs is hampered by challenges in production yields and stability. Engineered bacterial therapeutics is a unique approach being explored to overcome these issues by using bacteria to produce and deliver therapeutic compounds at the body site of use. A key advantage of this technology is the possibility to control drug delivery within the body in real time using genetic switches. However, the performance of such genetic switches suffers when used to control drugs that require post-translational modifications or are toxic to the host. In this study, these challenges were experienced when attempting to establish a thermal switch for the production of a ribosomally synthesized and post-translationally modified peptide antibiotic, darobactin, in probiotic E. coli. These challenges were overcome by developing a thermo-amplifier circuit that combined the thermal-switch with a T7 RNA Polymerase and its promoter that overcame limitations imposed by the host transcriptional machinery due to its orthogonality to it. This circuit enabled production of pathogen-inhibitory levels of darobactin at 40{degrees}C while maintaining leakiness below the detection limit at 37{degrees}C. More impressively, the thermo-amplifier circuit sustained production beyond the thermal induction duration. Thus, raised temperature for 2 h was sufficient for the bacteria to produce pathogen-inhibitory levels of darobactin even in the physiologically relevant simulated conditions of the intestines that include bile salts and low nutrient levels. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/579303v2_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@1cdb311org.highwire.dtl.DTLVardef@1a7523aorg.highwire.dtl.DTLVardef@77b68org.highwire.dtl.DTLVardef@136f52b_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗